Method and apparatus for treating fibrous materials



Get. is, 1927.

A T. L. DUNBAR METHOD AND APPARATUS FOR TREATING FIBRoUs MATERIALS Oct.1927.

18 .1'. L. DUNBAR METHOD AND APPARATUS FOR TREATING FIBROUS MATERIALS:Emg Q En;

'I In l G $5 INVENroR.

Hrrorm'ev.

Oct. 1 1927.

8 T. l.. DUNBAR METHOD AND APPARATUS FOR TREATING FIBROUS MATERIALS.222m 9oz 2 SMS HrroRNeY.

Patched a'. 1s, 1927.

1,646,084l UNITED STATES PATENT OFFICE.

THOMAS L. DUNBAR, 0F WATERTOWN, NEW

NEERING AND MAN UFACTUBING COMPANY, OF WATEBTOWN, NEW YORK, A COR-PORATION OF NEW YORK.

Yonx, AssIoNon To s'rnnnms ENGI- METHOD AND APPARATUS FOB TBEATINGFIBROUS MATERIALS.

Application led September 3, 1926. Serial No. 138,502.

This invention relates to improvements in the methods and apparatus fortreating fibrous material, such as wood pulp for the manufacture ofpaper, and one of the ob- 6 jects is to provide a novel process formanufacturing chemical kpulp and for reclamation of waste liquors. Theterm reclamation applies to the spent liquors which are drained from thepulp after the same has l0 been cooked, and which today are a source ofpollution to the streams. These spent liquors contain a high percentageof chemica s which are useful if properly handled.

Another object of my invention is to digest the pulp fiberswith anadmixture of normal cooking liquor and spent liquor, or the spent liquoralone may be used as a precooking1 agent and as a solvent for breakingdown t e mmic substances in woods. This is accomp ished both by asolvent and a catalytic action.

A further object of the invention is to provide a process in which thepressure in the digester can be raised as high as desired 5 by pumpinfresh additional acid into the digester an thereby permitting thereduction of steam, which is usually employed to obtain the highpressure necessary. The ver high pressure obtained by my method isdeslrable in the cooking of pulp, as it per' mits the temperature on thedigester/to be maintained at a low point, that is, at a low temperature'during the process of cooking. Heretofore, it has been thoughtimpossible to synchronize a low temperature with a high pressure sinceit has been necessary to create pressure by means of saturated-steam,which obviously increases the temperature. In my process, 'practically-any pressure can 40 be maintained, and the temperature can accordinglybe controlled, thus very materially reducing the cost of steam consution. and increasing the strength and improving the general ualities ofthe chemical pulp.'

46 A furt er object of the invention is to provide an apparatus topermita counter current liquor pumping eii'ect in the cooking ofdigesters.

In order to eliminate all waste of the spent liquor drained from thepulp. I propose to utilize this spent liquor in combination with analkaline solution, there being suflicient sulphur in the spent liquortov form sulphides. in combination with the alkaline culated in eitherdirection t liquor, thus creating a liquor which will cook what 1s knownto the trade as a modif fied sulphate pulp.

The following detail description taken in connection with theaccompanying drawings, is for use in sulphite cooking, but the methodand apparatus can be used in any pulp cooking process to which they areapplicable.

Referring to the drawings:

Fig. 1, is a side view of one form of my improved apparatus.

ig. 2, is a similar view of a modification employed for thecounter-current circulation of the acid. This form of the apparatusincluding two equalizers. f

Fig. 3, is a. side view of a further modication employing thecounter-current circulation principle with the use of a singleequalizer.

In using the ap aratus vshown in Fig. 1 for my process, tiie storage andrecovery tanks 1 and 2 may contain a mixture of normal cooking liquorand ent liquor in such proportions as are desiragle for the particular oration at hand. This mixture is force by pum liquor tank 5 w ere it ispreheated before it is fed by way of .ipe 6 into one or more of thesurge tanks g. 8 and 9. From either of the surge tanks, the liquormixture flows by gravit through pipe 10 and strainer 11 into thedigester 12. ssuming that the digester No. 1 is to be cooked, steam isturned into the same by the usual steam feeding pipe, (notC shown) andthis will tend to raise the pressure and heat up the pulp and liquor inthe digester; an gas passing olf b way of the p1pe-10 an surge tank intotli'e usual vent pipe 13 which conducts the same to the recovery stem.After the .digester has been broug t to normal cookin I pressure, thesteam is ractically cut oil', an' the pump 14 at the libttom of the distel is put in operation to force the iquor through the strainer 11 andpipe 10 into the surge tank, from which it may be passed by way of pipe15 back to the inlet of the pump. In this way the li uor may be c1rrough the pulp a number of times. l p.

The apparatus is so constructed that the liquor. thus pumped, may, ifdesired, be forced through the pipe 6 from one` surge 3 and) pipe 4 tothe hot i tank to the next, or back into the hot liquor tank 5. s eachdigester has its own pump 14, a similar operation may take place withany digester, and the operation may be intermittent or continuous fromone di ester to another, until the chips or other fi rous materialundergoing treatment, have practically exhausted the strength of theliquor. At this time, or at any other desired time, fresh strong liquorcan be forced by pump 16 into either surge tank and circulated throughone digester as a unit, or continuously through any number of digestersuntil the strength of the liquor in the digester or digesters has beenbuilt up to any desired omt. By pumping fresh additional liquor to thedigester lt])1y{"way of pump 16, pipe 6 and the Isurge ta the pressurein the digestermay be raised. The high pressure thus obtained is highlydesirable 'in the digestion of pulp, since it permits the temperature onthe digester to be maintained at a low point, which has been onedesideratum in the industry for many years. With my method andapparatus, practically any pressure can be maintained in the digester ordigesters, and the temperature can accordingly be controlled, thusverymaterially reducing the cost of steam consumption, and increasingthe strength and improving the general qualities of the chemical pulp.

This method may be pursued until the chips have been thorough y pulped,leaving a strong liquor in solution with the pulp at the termination ofthe end point of digestion. At this time the liquor may be drained olffrom the pulp through strainers 17 and the pipe 18 to the spent liquortank 19, where it is ready for a re-use.

Only about 50% of the amount of spent liquor drained from the pulp canbe used again through this cooking process, consequently, there'isabout'50% ordinarily following such procedure, that would be wasted. Inorder to eliminate all waste, I propose to utilize this spent liquor incombination with caustic soda, there being enough sulphur in the spentliquor to form sul hide of sodium in` combination with an al alineliquor, creating a liquor which will cook a modified sulphate pulp.

In order to reclaim this spent liquor, I pass the same by way of pipe 20to a soda.I mill where it is combined with caustic soda.

It may be said that an admixture of normal cooking liquor and spentliquor alone can be used as a pre-cooking agent, and as a' solvent forthe breaking down of the gummic substances in woods. Consequently, by

my process, tion of streams, but'I utllize the waste hquor, and thusreduce the cost of operating this system.

In the apparatus shown in Flg. 2, I have a system to permitcounter-current circula- I not only eliminate the pollu-A tion of theliquor throu h the digesters, and for this purpose, I com ine with thedigesters, two equalizer tanks 25 and 26. After the pressure has beenraised in the digesters to a proper degree, the pump 27 may be starteand this will force liquor from the e ualizer 25 `upwardly through thedigester o. 1, from which it may be discharged by way of pipe 28 intothe lower end of digester No. 2. It leaves the upper Aend of thisdigester by pipe 29, which conveys it to the lower portion of di esterfrom digester No. 3 y Way of pipe 30 into the equalizer tank 26. Inthisy wa from equalizer No. 1 may be-trans erred by an upward flowthrough each one of the digesters. Then it kmay be returned fromequalizer No. 2 by way of pump 31. This pump forces it upwardly throughdigester No. 3, from which it is discharged by pipe 32, which leads theliquor intoy the lower end of digester No. 2. The liquor flows upwardlyin digester No. 2 and may be discharged rom the top of the same throughpipe 33 which leads it back to the lower en of digester No. 1. It flowsby pipe 34, from the upper end of digester No. 1 to the equalizer 25.

By properly lines connecting the direction of sired.

In using this form of the apparatus, the digesters are started cookingwith equalizer No. 1 partly filled with liquor, while equalizer No. 2 isempty. The pressure in the digesters is brought up to the proper point,and the pump 27 is then employed to introduce strong liquor intodigester No. 1. equalizer No. l is filled up to the pipe 34, then it isobvious that the circulation in equalizer No. 1 may be in eitherdirection, and by properly controlling the valves in the pipe lines, theliquor mayT be moved either upwardly or downwardly, through eachdigester. A continuation of this operation can be maintained untildigestion has been completed, and the digesters are ready to blow oilgas, at which time fresh liquor is pumped from the storage tank into amixing tank, (not shown) and this fresh liquor is intermingled with hotgas vented ofi' through pipe 35. In the mixing tank, the hot gas may beabsorbed by fresh liquor, and will thereby heat this liquor up forsucceeding cooks.

Uniform recovery pressure is maintained during the cooking o eration bybleeding back to the storage tan from the equalizers through pipe 36.

In the embodiment illustrated in-Fig. 3, a single equalizer 50 isemployed; This equalizer will be partially filled-with fresh liquor, andwhenever desired, this liquor is forced from the lower end of theequalizer by pump controlling the valves in the the digesters andequalizers, flow may be varied as de- No. 3. It flows liquor dan 'through t e pulp after a 51, through a pipe 52 into the lower end ofdigester No. 1. It passes up through the -pulp in this digester, and isthen discharged from the upper end of the digester by way of pipe 53which leads it to the lower end of the digester No. 2. The liquor willpass up through this digester and be discharged by wa of pipe 54 whichwill lead it to the lower end7 of digester No. 1. The liquid may then,if desired, be discharged from this digester by way of pipes 55, 56 and57, back into the equalizer tank. Instead of operating the apparatus inthis manner, the pump 51 may force the liquor through pipe 58 into thelower end of the digester No. 2, and the liquor may be discharged fromthe upper end of this tank, either by way of pipe 59 or ipe 54. Witheither method, the liquor will lie fed from the equalizer back into theequalizer.

From the foregoing, it isbelieved that the essentials of the presentinvention may be readily understood, and it may be obvious to thoseskilled in the art, that changes may be made in the details disclosed,without departing from the s irit of the invention as expressed in the caims.

What I claim and desire vto ters Patent is:

1. In a chemical pulping process,

secure by Letheating fresh liquor to a `predetermined temperay digesterture, then pumping the same into a during the cooking process, to buildup a relatively high pressure in the digester, and maintaining arelatively low temperature in the digester while creating said pressure.

2. In a chemical pulping process, bringin the contents of afdigester toa predetermined temperature while pum ing fresh additional iquor intocontact witli the pulp to create a high pressure.

3. In a chemical pulping process, digesting the pulp with liquor in aclosed chamber at a predetermined temperature, and increasing thepressure in said chamber during the digestion by forcing fresh liquorheated toY a predetermined point into said chamber.

4. In a chemical pulping process, digesting the pulp with liquor until apredetermined pressure is reached, and then circulating hot fresh liquorthrough the pulp.

5. In a chemical pulping process, digesting the pulp with liquor at arelatively low temperature, and lunder hi h pressure, and circulatinfresh liquor in eated condition predetermined pressure has been reached.

6. In a chemical pulping process, heating fresh liquor to apredetermined temperature, and circulatin said heated li uor incountercurrent directions through t e pulp, while the latter isundergoing cooking.

7. In an apparatus of the class described,`a digester, a surge tank, apipe connecting the digester to the surge tank, and adapted to feedliquor by gravity from the tank to the digester, a hot liquor tank, andmeans for forcing hot liquor from the last mentioned tank to the surgetank.

8. An apparatus of the class described, 1ncluding a digester, a sur etank, pipes connecting the upper and ower ends of the digester to saidsurge tank, a pump interposed in one of said pipes for circulatingliquor through tlie surge tank and d1gester,a hot liquor tank, and meansfor feeding hquor from the last mentioned tank to the surge tank'.

9. In an apparatus ofthe class described, a storage tank, a. hot liquortank, means for forcibly feeding from the storage tank to the "hotliquor tank, a surge tank, means for feeding liquor from the hot liquortank to the surge tank, a digester a pipe connecting one end of thedigester to the surge tank, another pipe connecting the other end of thedigester to said surge tank, and a pump interposed in one of the lastmentioned pipes for circulating liquor through the digester and surgetank.

10. An apparatus as claimed in claim `9, including a bleed pipeconnecting the surge tank to the storage tank.

11. An apparatus of the class described, including a plurality ofdigesters, a plurality of surge tanks, a pair of pipes connecting eachdigester to its associated surge tank, pumps in certain of said pipesfor circulating liquor through the surge tanks and digesters, a hotliquor tank, a pipe connecting the hot liquor tank to the surge tanks,and means for forcing liquor from the hot liquor tank through the lastmentioned pipe.

12. An apparatus as claimed in claim 11, in which liquor may be forcedby one of said pumps from a surge tank to a digester, another one ofIthe surge tanks, or to the hot liquor tank.

13. An apparatus of the class described. including a storage tank, a hotliquor tank, means for forcibly feeding liquor from the storage tank to-the hot liquor tank, a surge tank, means for feeding liquor from thehot liquor tank to the surge tank, a digester, a pipe connecting one endof the digester to the surge tank, another pipe connecting the other endof the digester to the surge tank, and a pump interposed in one of thelast mentioned pipes for circulating liquor through the digester and sure tank.

In testimony whereof, I a x my signature at Watertown, New York, this30th day of August, 1926.

THOMAS L. DUNBAR.

